1. Field of Invention
The invention relates a serial multiplexer module, and in particular to a serial multiplexer module suitable for use in a server management system.
2. Related Art
In recent years, the Intelligent Platform Management Interface (IPMI) has been widely used in the server-related systems, and that is used to provide a cross platform interface to monitor most of the conditions of a server (for example, the voltage, system temperature, and the rotation speed of the heat dissipation fan), so that the management software provided by the various providers can be run on the various firmware and hardware platforms.
In general, in the framework of Intelligent Platform Management Interface (IPMI), the central portion is composed of the Baseboard Management Controller (BMC). Thus, BMC is utilized to monitor, control and manage the server systems through the various interfaces, and to achieve external communication through network ports or serial ports to transmit/receive external data packets.
In this respect, refer to FIG. 1 for a schematic diagram of the basic structure of a Baseboard Management Controller (BMC) according to the prior art. Usually, plural sets of Inter-Integrated Circuit (IIC/I2C) interfaces are provided in a BMC 100, to read the system detection value and record the related data, and are utilized to connect to the outside GPIO controller via the General-Purpose Input/Output (GPIO) pin G, thus further expanding the detection function of the system.
In addition, IPMI can be utilized to communicate with the outside control unit, such as the various sub-systems of the Peripheral Management Controller (PMC), management storage equipment or hard disk baseboard, by making use of the Intelligent Platform Management Bus (IPMB) of the IIC interface 12C.
Furthermore, usually the low pin count (LPC) interface is utilized in most of BMC 100 as the data transmission interface, and is mainly used to communicate with the central processing unit (CPU). Alternatively, the parallel address/data bus and the system management bus may be utilized in place of the LPC interface.
Usually, BMC is provided with a plurality of analog-to-digital converters (A/D converter) for monitoring the operational voltage, and counters for monitoring the fan speed, the pulse width modulation (PWM) or the D/A output of the fan driven, and the universal input/output (I/O) port, serial port and 12C bus used for connecting to the outside inductor and component interface expansion. Since BMC and its outside interface elements may be operational by remaining in the standby state. Thus, BMC may be used to provide continuously the management functions, regardless of the power supply condition of the system.
Moreover, the serial/modem interface is defined, so that the system manager may receive the IPMI message directly from IPMI or through a modem, namely, the serial port SP of BMC 100 may be utilized as the communication channel to receive or transmit orders or commands. In other words, RS-232 interface is used to introduce BMC 100, so that the manager at the remote end may utilize the programs at the terminal to execute the command sequence to manage the system through a serial port SP of BMC 100. Alternatively, the serial port SP of BMC 100 may be bridged to a serial port of a controller (for example, a serial port on the serial input/output (I/O) controller, or a serial port on the floppy disk controller) of a system, so that the frame images of the console may be output to BMC 100 via the serial port of the system. As such, the data of console may be transmitted to the manager at remote end from BMC 100 through a local area network (LAN).
From the above discussion, it is evident that, in the management of the server systems, BMC can be utilized to achieve the management of console through serial/modem interface or LAN.
Next, refer to FIG. 2 for a block diagram of a serial multiplexer module according to the prior art, wherein, the BMC 100 is utilized to proceed with the switching between the above two control modes through a serial multiplexer module 110. In case that LAN is utilized to execute the management of the system, the serial port SP of BMC 100 is connected to the serial port SP of floppy diskette controller 210 of the system 200 by means of the serial multiplexer module 110. At this time, the normal console redirection is obtained by BMC 100 from SiO 210, so as to introduce BMC 100 into LAN, thus enabling the system manager at remote end to proceed with the management of the system through LAN.
However, in case that serial connection is utilized to proceed with the management of the system, then the serial port SP of BMC 100 is switched and connected to a serial transceiver 200 (such as RS 132 transceiver) of the system 200 by means of the serial multiplexer module 110, so that the system manager may issue order or command to BMC 100 through the serial connection to proceed with the management of the system. In this case, the serial transceiver 220 is used to receive the serial communication signals from the communication port (COM port) 222 (for example, the DB9 communication port), and transmit the serial communication signals through the communication port (COM port) 222.
In the prior art, the serial multiplexer module 110 is composed of three respective multiplexers 112,114, and 116 having 8 fan-ins and 4 fan-outs as shown in FIG. 2. Wherein, each of the multiplexers 112,114, and 116 is provided with two input terminals (hereinafter referred to as the first input terminal A and the second input terminal B), output terminal and a control terminal. Among them, the control terminal is connected to the GPIO pin G of BMC 100, and the output terminal is connected to the serial port SP of BMC 100, the serial port SP of SIO 210, and the serial transceiver 220 of system 200. The first input terminal A of the multiplexer 112 is connected to the first input terminal A of the multiplexer 114, while the second terminal B of multiplexer 112 is connected to the first terminal A of multiplexer 116 and the serial port SP of SIO 210, and the second input terminal B of multiplexer 114 and the second terminal B of multiplexer 116 are connected to each other. However, the production cost for realizing such a serial multiplexer module 110 is rather high, besides, its structure is rather complex. Thus, the construction and configuration of the existing serial multiplexer module has much room for improvement.